Add initial reference spec

package.json

@@ -52,7 +52,8 @@
     "pdf-guide": "node docs/generate.js",
     "website": "node docs/generate_website.js",
     "docs": "npm run pdf-guide && npm run website && npm run browser-demo",
-    "test": "jest -i"
+    "test": "jest -i",
+    "test:unit": "jest unit/ -i"
   },
   "main": "js/pdfkit.js",
   "module": "js/pdfkit.es5.js",

tests/unit/reference.spec.js

@@ -0,0 +1,96 @@
+const PDFDocument = require('../../')
+const zlib = require('zlib')
+
+describe('PDFReference', () => {
+  let document
+  beforeEach(() => {
+    document = new PDFDocument()
+  })
+
+  test('instantiated without data', () => {
+    const ref = document.ref()    
+
+    expect(ref.id).toBeDefined()          
+    expect(ref.data).toBeDefined()
+    expect(ref.data).toBeInstanceOf(Object)          
+  })
+
+  test('instantiated with data', () => {
+    const refData = {Pages: 0}
+    const ref = document.ref(refData)            
+
+    expect(ref.id).toBeDefined()      
+    expect(ref.data).toBe(refData)        
+  })
+
+  test('written data of empty reference', (done) => {
+    const dataLog = []
+    const expected = [
+      '7 0 obj', 
+      '<<\n>>', 
+      'endobj'
+    ]
+    const ref = document.ref()
+    document._write = function(data) {
+      dataLog.push(data)
+    }
+    ref.finalize()
+    setTimeout(() => {
+      expect(dataLog).toEqual(expected)
+      done()
+    }, 1)
+  })
+
+  test('written data of reference with uncompressed data', (done) => {
+    const dataLog = []
+    const chunk = new Buffer('test')
+    const expected = [
+      '7 0 obj', 
+      `<<
+/Length ${chunk.length}
+>>`,
+      'stream',
+      chunk,
+      '\nendstream',
+      'endobj'
+    ]
+    const ref = document.ref()
+    ref.compress = false
+    ref.write(chunk)
+    document._write = function(data) {
+      dataLog.push(data)
+    }
+    ref.finalize()
+    setTimeout(() => {
+      expect(dataLog).toEqual(expected)
+      done()
+    }, 1)
+  })
+
+  test('written data of reference with compressed data', (done) => {
+    const dataLog = []
+    const chunk = new Buffer('test')
+    const compressed = zlib.deflateSync(chunk);
+    const expected = [
+      '7 0 obj', 
+      `<<
+/Length ${compressed.length}
+/Filter /FlateDecode
+>>`,
+      'stream',
+      compressed,
+      '\nendstream',
+      'endobj'
+    ]
+    const ref = document.ref()    
+    ref.write(chunk)
+    document._write = function(data) {
+      dataLog.push(data)
+    }
+    ref.finalize()
+    setTimeout(() => {
+      expect(dataLog).toEqual(expected)
+      done()
+    }, 1)
+  })
+})